Improved Liquid-Chromatographic Determination of Cyclosporine, with Concomitant Detection of a Cell-Bound Metabolite

This unique extraction and isocratic “high-performance ” liq-uid chromatographic method for measuring cyclosporine (CsA) in blood involves a Zorbax#{174}cyanopropyl analytical column maintained at 58 #{176}C,with detection at 214 nm, and recycling of the water:acetonitrile mobile phase for improved long-term column stability and efficiency. Routinely, 1.0 mL of serum, plasma, or whole blood is diluted with water:acetoni-trUe (70:30) and applied to a disposable solid-phase cyano-propyl column to rapidly extract the drug and the internal standard cyclosporin D (CsD). Analytical recovery for this step averages 90 % with whole blood and 98 % with serum and plasma. Between-run CVs were 6.5 and 2.6 % for means of 104 and 1128 g/L, respectively. The standard curve is linear up to 1600 g/L. The minimum detection limit is 10 to 15 g/L. No interferences from endogenous substances o